The present invention relates to an innerseal for a container and more specifically to an innerseal which is secured to the mouth of a container and which has an integrally formed pull tab and cut-out portions in the circular periphery of the seal to ensure that the entire seal can be removed without tearing.
Small glass jars may be generally provided with a screw-type cap with an innerseal which is glued around the entire periphery of the mouth of the container. The innerseal provides an oxygen moisture barrier film and in use with certain products such as coffee also provides a vacuum seal. The inner seal is removed by pulling a pull tab which is integrally formed with the innerseal and extends from the circular periphery of the seal. However, when relatively thin laminate seals are used to seal wide mouth jars, quite frequently the seal cannot be completely removed readily because of tearing of the seal material. This tearing may be due to small nicks or cuts at the edges of the pull tab or due to damage to the corners of the tab caused by an overhang portion of the seal which extends over a portion of the outer face of the mouth of the container. Tearing may also occur due to the degree of tension in the thin laminate seal when the pull tab is grasped to remove the innerseal. While higher tension without tearing of the innerseal could be achieved by using thicker laminate seals, it is preferable to utilize seals having a thickness in the 3 to 5 mil range. Furthermore, the use of thicker laminates for the innerseal would not necessarily solve the problem of tearing of the seal due to nicks and cuts at the edges of the pull tabs.
Innerseals may be formed from a laminate of a polyester film to give the innerseal strength, a foil for moisture protection and paper or like material to provide body for the laminate. The innerseal is cut from a sheet of laminate in a two step process. The pull tab is initially cut and folded over to be within the circumference of the innerseal. The second step in the process is to simultaneously cut both the circular innerseal and a pulpboard liner. This second circular cut of the innerseal may result in nicks or cuts at the points of intersection between the pull tab and the circular portion of the innerseal. The pulpboard liner and innerseal are then forced into the container screw cap beneath a retention bead in the screw cap and simultaneously with this operation the inner liner and pulpboard liner are heated so that the wax surface of the pulpboard liner is melted and seals to the innerseal. Following this step, the upper surface of the mouth of the container is provided with glue and the screw cap is screwed tightly into engagement with the container so that the innerseal is glued to the entire upper face of the mouth of the container. Due to the pressure applied to the screw cap as it is screwed onto the container, the pulpboard liner is compressed. The innerseal has a diameter slightly larger than the outer diameter of the mouth of the container and the compression of the pulpboard causes the outer periphery of the innerseal to overhang and seal to the other surface of the mouth of the container. As the outer periphery of the innerseal is drawn downward around the outside face of the container, a cut or tear may occur between the outer edges of the pull tab and the circular periphery of the innerseal.
In use, the container cap is unscrewed to release the wax seal of the pulpboard liner from the innerseal which is glued to the mouth of the container. The pull tab on the innerseal is then grasped and pulled upwardly to release the innerseal from the mouth of the container. As noted hereinbefore, in the area between the overhang and the pull tab there is likely to be a cut or tear in the innerseal caused by the die cutting operation or due to the overhang of the circular periphery of the innerseal damaging the edges of the pull tab. Thus, when the pull tab is lifted the innerseal may be torn so that the entire innerseal is not lifted from the mouth of the container in one piece.